Ten sailors have been injured after a regatta in Northern Ireland was hit by a squall.

The casualties were mostly suffering from the effects of hypothermia after more than 200 people competing in 87 sailing dinghies were hit by a sudden change in the weather on Strangford Lough, the Maritime and Coastguard agency said.

Initial reports suggested scores of people ended up in the water after a spate of capsizes but Coastguard chiefs later scaled back the figures saying 20 people were believed to have gone overboard.

Among the injured were two teenage boys, a woman, believed to be in her 30s, who injured an arm, and another sailor who suffered a head injury.

It is understood one person was in the water for about 20 minutes and most of those who ended up in the water were treated for the effects of hypothermia.

Two people with minor injuries were taken to the Ulster Hospital in Dundonald, on the outskirts of east Belfast, after being treated by paramedics at the East Down Yacht Club near Killyleagh.

The dinghies hit by the squall had been competing in the GP14 World Championships with competitors from local clubs, the Irish Republic, England and Australia among other countries.

Belfast Coastguard was first contacted just before 2pm reporting that some of the boats had capsized, while others were struggling to cope in the strong winds and squally showers.

Liam Colquhoun, watch manager at Belfast Coastguard, confirmed the search and rescue operation had been a success and was called off within three hours.

"We have now been told by our rescue units on scene that everyone has safely returned to shore and that no one is missing," he said.

"We believe 20 people ended up in the water after their boats capsized this afternoon, 10 of them requiring medical attention.

"The weather conditions on scene have been pretty treacherous, with winds gusting up to 60mph. We're very thankful that everyone has now safely returned."

The Bangor and Portaferry Coastguard res cue teams, the Portaferry and Newcastle RNLI lifeboats, the Irish Coast Guard helicopter with the helicopter from RAF Valley were sent to the scene.

Ambulance crews set up tents to treat the injured at the shoreline.

The South Eastern Health and Social Care Trust in Northern Ireland launched a major incident and emergency response plan after reports of the squall hitting the regatta.

The GP14 races were due to run until Friday.

Two races had been due to be held today but only one was completed before the squall struck dozens of boats competing around islands about three miles offshore.

Strangford Lough is an area affected by powerful tides and currents. It is a short distance south west of Belfast in Co Down and is popular with all sorts of watersports enthusiasts and a dedicated canoe trail has been laid out along its waters.

Organisers of the GP14 had attempted to begin racing yesterday but after putting out on to the water the event was called off when rain and strong winds associated with the tail end of former Hurricane Bertha created choppy seas which they said "caught out some of those less used to" the lough.

Four boats capsized on Sunday and two suffered damaged rudders before the competition was postponed.

A spokesman for the East Down Yacht Club said two competitors suffered suspected broken limbs.

He said no-one else was seriously injured while a number of sailors suffered nothing more than cuts, scratches and bruises "consistent with the sport at this level".

The club confirmed 88 racing boats were on the water when the weather turned.

Towards the finish of the first race, which began at about midday, the race officer decided that with worsening weather conditions the second race would be cancelled, the spokesman said.

"The fleet started to head inshore when a strong squall of 31 knots passed over the race area," he said.

"The effect of this was that some of the GP14 boats capsized. This is not an unusual situation and crews are trained on how to right their boat.

"Unfortunately a further stronger squall registering 37 knots followed the first, capsizing a further number of the fleet."

The EDYC spokesman said media reports of 80 boats capsizing were incorrect as there were no more than 10 to 12 capsized at any one time.

"The capsizes were successfully handed by competitors and 13 safety boats accompanying the race," he said.

The EDYC said that the race officer contacted the Coastguard as a precaution amid concerns that conditions on the race site could have worsened.

One of the competitors, Tom Daniel, 20, from Halifax in Yorkshire, said his boat overturned twice but that reports of the danger to sailors had been blown out of proportion.

"A massive squall came through, a lot of boats went over. We got very wet, a few got various knocks and bumps going over but nothing serious," he said.

"A bit further along the line a lot of people went in because a massive squall came in and we ended up back in.

"We thought somebody was seriously hurt. We thought there was more damage than there was because a few people did look like they were struggling but it is part of the sport and this would not normally attract too much attention but people from the shore saw that there was damage and it has been blown out of proportion."

Mr Daniel said the wind was not extreme.

"The guys coped with it very well but some people did struggle a bit," he said.

The sailor estimated he saw around 30 people go into the water.

He added: "Someone looking from shore saw all the boats go over but most of the people out there knew exactly what they are doing, people capsize regularly."

Experienced sailor Lucia Nicholson, from Sligo in the west of Ireland, said they had been on the water for about an hour-and-a-half.

She said some of the main competitors had an extra sail, which could have made them more vulnerable to the squall.